The present invention relates to pesticide compositions. In particular, the present invention relates to pesticide compositions comprising a pesticide and a redispersible polymer. The present invention also relates to a method for controlling agricultural pests by applying to the pest or the locus of the pest a pesticide composition comprising a pesticide and a redispersible polymer.
Compositions intended for the control of agricultural pests are typically applied by spraying a composition comprising the pesticide using water as a carrier liquid. For this reason, pesticide compositions are supplied to the grower in formulations which are intended to be dissolved or dispersed in water. These formulations may be liquid formulations such as aqueous solutions or emulsifiable concentrates or solid formulations such as wettable powders or granular formulations. Solid formulations have many advantages over liquid formulations in terms of cost, storage, and packaging, including disposal of packaging.
Biological efficacy of pesticides is influenced by many factors, particularly the residence time of the pesticide on the treated surface, which is often a plant leaf surface. A major factor influencing the residence time is the degree to which the pesticide resists wash-off by rain, that is, rainfastness. With liquid formulations, rainfastness may be improved by including ingredients in the formulation or adding such ingredients to the spray tank (tank mixing) that, during drying, provide a water-resistant bond between the pesticide and the substrate. For example, emulsified oil or water insoluble polymers prepared in emulsion have been used to improve liquid formulation rainfastness. One widely used material is a formulation comprising a carboxylated synthetic latex emulsion polymer, a primary aliphatic oxyalkylated alcohol, and water. This material has been shown to improve the efficacy of a variety of pesticides. However, because it is a liquid formulation, it cannot be used as a component of a solid pesticide formulation.
Solid formulations present a different set of competing problems when compared to liquid formulations. In order for solid formulations to readily disperse in water, water-resisting additives cannot be used in the formulation. In fact, high levels of water soluble dispersants are typically required so that the solid formulation will disperse in the spray tank. Although emulsified oil or water insoluble polymers prepared in emulsion have been used with liquid formulations or in tank mixes, none has been described that address the problem of improving rainfastness of solid formulations without requiring a separate tank mix additive. This is both inconvenient and problematic for the grower who desires to use a dry, solid pesticide formulation. Dry solid formulations are particularly important because they can be more easily stored, packaged, and transported than their liquid counterparts. Therefore, there is a continuing need for additives which are compatible with solid pesticide formulations.
We have discovered that redispersible polymers may be used as pesticide additives. Redispersible polymers are solid compositions which incorporate water insoluble polymers prepared in emulsion combined, prior to drying, with water soluble polymers. Such compositions are typically isolated by spray drying and the products are referred to as redispersible powders. The water soluble polymer is critical for redispersion of the water insoluble polymer. These polymers overcome many of the problems associated with the use of emulsion polymers as adjuvants in solid pesticide formulations. In addition, they provide a surprising increase in the efficacy of many pesticides and improved resistance to wash-off by rain.
Thus, this invention provides a pesticide composition, comprising:
(a) one or more pesticides; and
(b) one or more redispersible polymers comprising:
(1) one or more water insoluble polymers prepared in emulsion; and
(2) one or more water soluble polymers.
The composition may further comprise other ingredients to aid in dispersibility of the pesticide in water, modify surface tension of the spray, and promote adhesion of the water insoluble polymers.
The term xe2x80x9cpesticidexe2x80x9d means a chemical which is intended to mitigate a pest including insects, weeds, fungi, and related organisms. For purposes of this invention, a pesticide can also include viruses, bacteria, or other organisms which can control pests and which are found or can be modified to form a stable particle. The pesticide preferably comprises 5 to 90% by weight of the pesticide composition. The pesticide of the composition of this invention may be in the form of a pure active ingredient, a technical grade of the active ingredient, or an active ingredient formulated with one or more agronomically acceptable carriers. By xe2x80x9cagronomically acceptable carrierxe2x80x9d is meant any substance which can be used to aid the dispersion of the active ingredient in the composition in water without impairing the active ingredient""s effectiveness and which by itself has no significant detrimental effect on the soil, equipment, desirable plants, or the agronomic environment. Pesticides in the form of particles are preferred. Most preferred are particles in the range of 0.1 to 20 microns in diameter.
The term xe2x80x9credispersible polymerxe2x80x9d means a free-flowing dry powder comprising one or more water insoluble polymers and one or more water soluble polymers, produced by drying an emulsion polymer dispersion, that redisperses readily in water but, when dried a second time, forms a water resistant film. Redispersible polymers are well known in the art. See, for example, U.S. Pat. No. 3,784,648 (RE 28,780) (water insoluble synthetic resins with a water soluble condensation product of melamine and formaldehyde which contains sulfonate groups); U.S. Pat. No. 5,536,779 (polymer powder derived from unsaturated monomers and at least one added starch-degradation product); U.S. Pat. No. 5,519,084 (acrylic emulsion polymers and polyvinyl alcohol); DE 4,402,408 (unsaturated copolymers and post-added protective colloids); JP 7,053,730 (acrylic emulsion polymers and colloid prepared from sodium styrene sulfonate and a polymerizing emulsifying agent); EP 632096 (acrylic and vinyl emulsion polymers with amino functional polyvinyl alcohol); U.S. Pat. No. 5,252,704 (acrylic and vinyl emulsion polymers with polyvinyl pyrollidone); U.S. Pat. No. 5,225,478 (emulsion polymers of olefinically unsaturated monomers with water soluble metal salts of phenolsulfonic acid/formaldehyde condensates); and EP 723975 (emulsion copolymers of styrene and alkyl(meth)acrylates with water soluble colloids).
Many redispersible polymers are two-stage emulsion polymers formed when a second-stage, water soluble polymer forms a xe2x80x9cshellxe2x80x9d or coating around a discreet domain or xe2x80x9ccorexe2x80x9d of the first-stage, water insoluble polymer. Examples of such core-shell polymers are disclosed in U.S. Pat. Nos. 4,916,171 and 5,403,894. In these examples, the water soluble polymer is a copolymer of methacrylic acid that is neutralized with base. U.S. Pat. No. 4,876,313 also discloses the use of polyfunctional compounds to partially graft or bond the water soluble and water insoluble polymers.
One embodiment of this invention provides a composition comprising a pesticide, formulated as a wettable powder, a dust, or a dispersible granule, and a redispersible powder comprising one or more water insoluble polymers prepared in emulsion and one or more water soluble polymers, such as those disclosed in the above references.
Another embodiment of this invention provides a wettable powder, a dust, or dispersible granule pesticide formulation comprising one or more pesticides and one or more redispersible polymers wherein the formulation is prepared by a process comprising the steps of:
a) combining a dispersion of the pesticide in water with one or more water insoluble polymers formed in emulsion and one or more water soluble polymers and
b) drying the combination.
Another embodiment of this invention provides a dry pesticide adjuvant comprising one or more redispersible polymers comprising:
(1) one or more water insoluble polymers prepared in emulsion; and
(2) one or more water soluble polymers.
Still another embodiment of this invention provides a method of controlling a pest comprising applying to the pest, the locus of the pest, or a food source of the pest a pesticide composition comprising:
(a) one or more pesticides; and
(b) a redispersible polymer comprising:
(1) one or more water insoluble polymers prepared in emulsion; and
(2) one or more water soluble polymers.
Preferred water insoluble polymers are polymerized in emulsion and have an emulsion particle size of 0.1 to 5 microns. In order to obtain the proper balance of properties, preferred water insoluble polymers are selected from one or more homopolymers and copolymers independently comprising polymer units derived from: (1) one or more acrylic ester monomers; acrylamide or substituted acrylamides; styrene or substituted styrenes; butadiene; vinyl acetate or other vinyl esters; vinyl monomers such as vinyl chloride, vinylidene chloride, N-vinyl pyrolidone; acrylonitrile, and methacrylonitrile wherein the water insoluble polymer has a glass transition temperature between 0 and 60 degrees Celcius (xc2x0 C.), preferably between 0 and 40xc2x0 C. and (2) ethylene and vinyl esters wherein the water insoluble polymer has a glass transition temperature between xe2x88x9220 and 40xc2x0 C. Acrylic ester monomers include, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, and hydroxypropyl acrylate. The preferred water insoluble polymer comprises monomer units derived from 2-ethylhexyl acrylate, butyl acrylate, ethyl acrylate, methyl acrylate, methyl methacrylate, styrene, and vinyl acetate. When the water insoluble polymer comprises units derived from vinyl acetate, a more preferred form of the polymer has more than 3% of the vinyl acetate units hydrolyzed by addition of an inorganic base. The water insoluble polymer preferably comprises 5-80% by weight of the pesticide composition.
Preferred water soluble polymers are non-ionic polymers wherein the non-ionic polymer has a molecular weight greater than 2,000 amu such as, for example, polymers and copolymers comprising units derived from one or more of polyvinyl alcohol, methyl methacrylate, and methacrylic acid. Polyvinyl alcohol or partially hydrolyzed copolymers of vinyl esters, for example, vinyl acetate, are preferred non-ionic polymers. The water soluble polymer preferably comprises 1-40% by weight of the pesticide composition.
The compositions of this invention often benefit from the presence of added surfactant. One skilled in the art will recognize circumstances where surfactants are typically combined with the pesticide to be applied. We have found that in some cases, the combination of surfactant and redispersible polymer provides an increase in biological activity of the pesticide beyond that which would be expected based on the biological activity of the pesticide in the presence of either the surfactant or the redispersible polymer alone. One possible explanation for this phenomenon is that the redispersible polymer provides improved resistance to washoff to the pesticide/surfactant mixture. Surfactants that may be employed in combination with redispersible polymers include one or more of various nonionic, anionic, and amphoteric surfactants. Examples of nonionic surfactants which are useful include polyalkylene glycol ethers and condensation products of alkyl phenols, aliphatic alcohols, aliphatic amines, and fatty acids with ethylene oxide, propylene oxide or their mixtures such as the ethoxylated alkyl phenols or ethoxylated aryl and polyaryl phenols and carboxylic esters solubilized with a polyol or polyoxyethylene. Anionic surfactants include salts of alkyl aryl sulphonic acids, sulphated polyglycol ethers, salts of sulfosuccinic acid esters with hydrophobes such as 2-ethylhexanol, salts of phosphated polyglycol ethers, alkyl sarcosine salts, alkyl isethionate salts, and derivatives of taurine. Additional benefit is provided by surfactants that improve the adhesive character of the redispersible polymer. Most preferred are solid surfactants which can be dry blended with the pesticide/redispersible polymer composition. Examples of such surfactants include dioctyl sodium sulfosuccinate, sodium lauryl sulfate, and fatty acid amides of N-methyl-taurine.
To further promote the formation of a film containing the pesticide on the surface to which the pesticide is applied, one or more additional film-forming aids may be added to the composition. Such aids include low molecular weight solids which are soluble in both water and in the polymer. Preferred film-forming aids include caprolactam and neopentyl glycol. Some solid surfactants, such as dioctyl sodium sulfosuccinate, may also serve as film-forming aids.
The compositions of this invention may be prepared in a variety of ways. One method is to mechanically combine the pesticide with the redispersible polymer, both components in the form of solids. This mixing process can range from as simple a procedure as physically blending the two solid materials together to as complex a process as blending the two components together with additional components and forming a granular material wherein the granular particles contain both components. Alternatively, the redispersible powder may be mixed with a dispersible granule forming a surface coating on the granule. The compositions can also be prepared by combining an aqueous dispersion of the pesticide component containing at least one of the water insoluble polymers with the water soluble polymer and then drying to solid form.
The redispersible polymer itself may also be added to the spray tank before or after addition of the pesticide.
For some applications, one or more pesticides may be combined in the compositions of the present invention, thereby providing additional advantages and effectiveness, including fewer total pesticide applications, than if the pesticides are applied separately. When mixtures of pesticides are employed, the relative proportions of each in the composition will depend upon the relative efficacy and the desired application rate of each pesticide with respect to the crops and/or weeds to be treated. Those skilled in the art will recognize that mixtures of pesticides may provide advantages such as a broader spectrum of activity than one pesticide used alone.